Electrical boxes are commonly used to provide electrical service at convenient locations within buildings. The electrical boxes are commonly formed of plastic or metal and are usually securely fastened by screws or nails to the framework to the building. In newly constructed buildings, the open face of the electrical box, in which an electrical device such as an outlet or switch will be mounted, is usually flush with the surface of the wall or ceiling in which it is installed.
When existing buildings are renovated or restored, it is common for renovators to lay down new sheet stock such as sheet rock, paneling, etc., over the existing ceilings or walls. This causes the existing electrical boxes to become recessed within the wall by the thickness of the new sheet stock.
To solve this problem, box extenders of several different types have been developed.